Tuesday, July 21, 2009

Transposable elements

What do you need to know about transposons?

Transposons may insert into a gene, thus disrupting it/interrupting it. Effectively, they can therefore be mutagenic.
Transposons do indeed 'jump', but they can typically do so only in a short window of time.
'Jumping' is less frequent than 'not jumping'.
When we deal with transposons, we introduce a significant amount of randomness...

You need to remember that a completely functioning transposon must have at least intact insertion sequences (inverted repeats) and a functioning transposase gene.
Examples of transposons are the corn Ac element, Drosophila P element, and many others. Although they all work based on the same principles, don't mix them up. (Flies also have a whole bunch of transposons with interesting names: hobo, gypsy, nomad, tyrant, and so forth).
There are mutated transposons that can't produce transposase anymore. In order for them to transpose (i.e. 'move'), another source of transposase is required.
Other mutated transposons can't move anymore because their IRs are not intact. However, they can still produce transposase.

You should be able to predict phenotypics frequencies in the offsprings of crosses between individuals that carry different versions of a transposable element (like in your Ac/Ds question).

You should also be able to diagnose the presence of a transposable element... remeber:
mosaicism ('patches'), a high mutation rate, and a high reversion rate are all indications that there might be a transposable element involved.

You will also need to know about hybrid dysgenesis and how to use P elements to make transgenic Drosophila and to clone a Drosophila gene: there is a handout on the 'parallel' 335 page.

PLEASE POST HERE ALL YOUR QUESTIONS ON TRANSPOSABLE ELEMENTS!

Posted by at

5 comments:

  1. AnonymousJuly 21, 2009 at 9:36 PM

    Hi Pam, I am not sure what is defined as the Insertion Sequence (I know, just a technical issue here, but I don't want marks to be lost because I state things wrong when I am thinking on the right track). Does it include the transposase gene? Or does it just include the Inverted Repeats at the end of the transposon?

    From what I understand from the textbook ((p. 492-493) an Insertion-Sequence Element is something that can be inserted (and to me that sounds like IRs+transposase), and a Transposon is an insertion sequence + any gene to be moved along.

    Thanks for taking the time to read this, and thanks in advance for clarifying these terms.

    ReplyDelete
  2. AnonymousJuly 23, 2009 at 12:05 AM

    Hi Pam, would it be possible to quickly review some key points about promoter and enhancer trapping? I'm a little confused as to why we would do a promoter/enhancer trap, and how the whole process is actually carried out.

    Thank you!

    ReplyDelete
  3. AnonymousJuly 23, 2009 at 2:21 AM

    for developmental genetics is the phenotype always the overall picture?

    ReplyDelete
  4. AnonymousJuly 23, 2009 at 9:29 PM

    Hi Pam,

    would it be possible to post the answer to the corn practice question on the Bio 335 website, in order to check our work?

    ReplyDelete
  5. AnonymousJuly 24, 2009 at 2:45 PM

    Hi Pam,

    I am not sure for the answers of last question in our final. I will really appreciate if you can you tell me the answers. I am really really worried and can't think of anything else. Sorry for bothering you again but Please!!!

    I know you are great:)

    How did everyone else did with the exam????

    ReplyDelete

Subscribe to: Post Comments (Atom)